U.S. patent number 5,242,991 [Application Number 07/821,835] was granted by the patent office on 1993-09-07 for quaternary ammonium polyarylamide.
This patent grant is currently assigned to E. I. Du Pont de Nemours and Company. Invention is credited to Robert R. Burch, Lewis E. Manring.
United States Patent |
5,242,991 |
Burch , et al. |
September 7, 1993 |
Quaternary ammonium polyarylamide
Abstract
Quaternary ammonium polyarylamides are provided that are useful
in articles of manufacture that require minimal ionic impurities.
The polyarylamides are produced by reacting certain polyamides
together with quaternary ammonium bases of the formula
R.sup.4.sub.4 N.sup.+ X.sup.-, wherein each R.sup.4 is
independently selected from hydrocarbyl or substituted hydrocarbyl,
provided that at least one of the R.sup.4 groups contains at least
one beta hydrogen atom. There is also provided the process for
producing the polyarylamides, the process for making articles of
manufacture from the polyarylamides, and a process for modifying
the surfaces of such polyamides.
Inventors: |
Burch; Robert R. (Exton,
PA), Manring; Lewis E. (Wilmington, DE) |
Assignee: |
E. I. Du Pont de Nemours and
Company (Wilmington, DE)
|
Family
ID: |
27034454 |
Appl.
No.: |
07/821,835 |
Filed: |
January 13, 1992 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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445956 |
Nov 28, 1988 |
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Current U.S.
Class: |
525/420; 525/419;
525/435; 525/452; 525/540; 528/342; 528/348; 528/68 |
Current CPC
Class: |
C08G
69/32 (20130101); C08G 73/0677 (20130101); C08G
69/48 (20130101); H05K 1/0346 (20130101) |
Current International
Class: |
C08G
69/32 (20060101); C08G 69/00 (20060101); C08G
69/48 (20060101); C08G 73/00 (20060101); C08G
73/06 (20060101); H05K 1/03 (20060101); C08G
069/48 () |
Field of
Search: |
;525/420,419,435,452,540 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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0121091 |
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Oct 1984 |
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EP |
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0309229 |
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Sep 1988 |
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EP |
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Other References
Takayanagai et al., J. Polym. Sci., Polym. Chem. Ed., vol. 19,
1133-1145 (1981). .
Takayanagai et al., J. Polym. Sci., Polym. Chem. Ed., vol. 21,
31-39 (1983). .
Bodaghi et al., Polym. Eng. Sci., vol. 24, 242-251 (1984). .
Aoki et al., Polym. Eng. Sci., vol. 20, 221-229 (1980). .
Flood et al., J. Appl. Polym. Sci., vol. 27, 2965-2985
(1982)..
|
Primary Examiner: Anderson; Harold D.
Parent Case Text
This is a continuation of application Ser. No. 07/445,956 filed
Nov. 28, 1989, now abandoned.
Claims
We claim:
1. A quaternary ammonium polyarylamide comprising a polyarylamide
derived from polymer repeat units independently selected from the
group consisting of ##STR4## wherein: R is selected from the group
consisting of R.sup.3 and R.sup.1 NHC(.dbd.O)R.sup.2,
R.sup.1 and R.sup.3, independently, are selected from the group
consisting of m-phenylene, p-phenylene, 3,3'-biphenylene,
3,4'-biphenylene, 4,4'-biphenylene and 4,4'-diphenyelene ether,
R.sup.2 is selected from the group consisting of R.sup.1 and
--CH.sub.2).sub.x,
Ar is 1,2,4-benzenetriyl, and
x is 1 to 10,
the polyarylamide having a molecular weight of at least about 2500;
and quaternary ammonium cations of the formula
wherein each R.sup.4 is independently selected from the group
consisting of hydrocarbyl or substituted hydrocarbyl, provided that
at least one of the R.sup.4 groups contains at least one beta
hydrogen atom.
2. The quaternary ammonium polyarylamide of claim 1 wherein all
R.sup.4 groups contain at least one beta hydrogen atom.
3. The quaternary ammonium polyarylamide of claim 1 having a degree
of deprotonation of 0.1-100 percent.
4. The quaternary ammonium polyarylamide of claim 1 wherein the
polymer repeat units are selected from the group consisting of
poly(p-phenylene terephthalamide), poly(m-phenylene
isophthalamide), poly(p-benzamide), poly(4,4'biphenylene
isophthalamide), poly(chloro-p-phenylene isophthalamide), the
polybenzimidazole of 3,4,3',4'-tetraaminobiphenyl and isophthalic
acid, and the polybenzimidazole of 3,4-diaminobenzoic acid.
5. The quaternary ammonium polyarylamide of claim 1 wherein the
polymer repeat units are selected from the group consisting of
poly(p-phenylene terephthalamide), poly(m-phenylene isophthalamide)
and poly(p-benzamide).
6. The quaternary ammonium polyarylamide of claim 1 wherein the
polymer repeat units are selected from the group consisting of
poly(p-phenylene terephthalamide) and poly(m-phenylene
isophthalamide).
7. The quaternary ammonium polyarylamide of claim 1 wherein the
quaternary ammonium cation has a molecular weight of less than
350.
8. The quaternary ammonium polyarylamide of claim 1 wherein the
quaternary ammonium cation has a molecular weight of less than
250.
9. The quaternary ammonium polyarylamide of claim 1 wherein the
quaternary ammonium cation is tetraethylammonium or
tetra-n-butylammonium.
10. The quaternary ammonium polyarylamide of claim 1 in solution in
a dialkyl sulfoxide.
11. The quaternary ammonium polyarylamide of claim 10 wherein the
dialkyl sulfoxide is dimethyl sulfoxide.
12. A process for the preparation of a quaternary ammonium
polyarylamide comprising contacting polyamides derives from polymer
repeat units independently selected from the group consisting of
##STR5## wherein: R is selected from the group consisting of
R.sup.3 and R.sup.1 NHC(.dbd.O)R.sup.2,
R.sup.1 and R.sup.3, independently, are selected from the group
consisting of m-phenylene, p-phenylene, 3,3'-biphenylene,
3,4'-biphenylene, 4,4'-biphenylene and 4,4'-diphenylene ether,
R.sup.2 is selected from the group consisting of R.sup.1 and
--CH.sub.2).sub.x,
Ar is 1,2,4-benzenetriyl, and
x is 1 to 10,
the polyamide having a molecular weight of at least about 2500;
with a solution of a quaternary ammonium base of the formula
wherein each R.sup.4 is independently selected from the group
consisting of hydrocarbyl or substituted hydrocarbyl, provided that
at least one of the R.sup.4 groups contains at least one beta
hydrogen atom;
and wherein X is an anion whose conjugate acid has a pKa greater
than that of the hydrogen attached to the amido group in the
unreacted polymer repeat units.
13. The process of claim 12 wherein said anion is hydroxide or
alkoxide.
14. The process of claim 12 wherein said solvent is a
dialkylsulfoxide.
15. The process of claim 14 wherein said solvent is
dimethylsulfoxide.
16. The process of claim 12 wherein R.sup.4.sub.4 N.sup.+ is
tetraethylammonium or tetra-n-butylammonium.
17. The process of claim 12 further comprising removing the
solvent.
18. The process of claim 12 carried out at a temperature of
0.degree.-60.degree. C.
19. The process of claim 12 carried out at a temperature of
20.degree.-40.degree. C.
Description
FIELD OF INVENTION
The present invention relates to quaternary ammonium polyarylamides
formed from quaternary ammonium bases and polyamides. More
particularly, this invention relates to quaternary ammonium
polyarylamides that, upon heating decompose to the parent polyamide
and volatile nonionic byproducts. The invention further relates to
processes for producing the quaternary ammonium polyarylamides and
making parts from them, and processes for modifying the surface
properties of polyamides.
BACKGROUND OF THE INVENTION
The preparation of alkali metal salts of polyamides and solutions
thereof in dimethylsulfoxide is well known. For example M.
Takayanagai and T. Katayose in J. Polym. Sci., Polym. Chem. Ed.,
vol. 19, 1133-1145 (1981) describe the preparation of the sodium
salt of poly(p-phenylene terephthalamide) (hereinafter PPTA) by the
reaction of sodium hydride in dimethylsulfoxide (hereinafter DMSO).
These sodium salts were used to N-alkylate the polymer by the
reaction of a polyarylamide with the appropriate hydrocarbyl
halide. The same authors used the same polyarylamides to graft
other polymers to PPTA, J. Polym. Sci., Polym. Chem. Ed., vol. 21,
31-39 (1983).
U.S. Pat. No. 4,785,038 describes the dissolution of polyamides in
solutions containing certain sodium or potassium bases, a liquid
sulfoxide, and water or an alcohol.
U.S. Pat. No. 4,824,881 describes a method for deprotonating
polyamides with an alkali metal alkoxide or amide to form a
polyarylamide polyanion solution in a liquid sulfoxide.
In all of the above references the only cations specifically
mentioned or used are alkali metal cations. There is no mention or
use of quaternary ammonium cations as the counterions for
polyarylamides. In order to form useful articles from the above
polyarylamide alkali metal salts it is necessary to neutralize the
salts and preferably remove as much of the ionic impurities (the
alkali metal salts from the neutralization) as possible, since such
ionic impurities are usually deleterious in the final use of such
parts. Even traces of such ionic impurities are especially
deleterious, for example, in electrical and electronic uses. It is
usually difficult to wash out the last traces of such ionic
impurities.
H. Bodaghi et. al., Polym. Eng. Sci., vol. 24, 242-251 (1984); H.
Aoki, et. al., Polym. Eng. Sci., vol. 20, 221-229 (1980); J. E.
Flood, et. al., J. Appl. Polym. Sci., vol. 27, 2965-2985 (1982) all
describe the preparation of films and other parts from sulfuric
acid solutions of PPTA. The "coagulants" used in these processes,
usually water or lower alcohols, serve not only to coagulate the
polymer from the sulfuric acid solution but also to wash the
corrosive and ionic sulfuric acid from the coagulated polymer.
It is an object of the present invention to provide quaternary
ammonium polyarylamides formed from quaternary ammonium bases and
polyamides. It is a feature of the present invention (to provide
unique polyarylamides) as well as processes for the preparation
thereof and for the development of polymeric articles, the
resulting polyamide articles being substantially devoid of ionic
impurities. An advantage of the present invention is its usefulness
in forming shaped articles having minimal ionic impurities, such as
electronic circuit boards and the like. These and other objects,
features and advantages of the present invention will become
readily apparent upon having reference to the following description
of the invention.
SUMMARY OF THE INVENTION
Quaternary ammonium polyarylamides comprising polyarylamides
derived from polymer repeat units independently selected from the
group consisting of ##STR1## wherein: R is selected from R.sup.3
and R.sup.1 NHC(.dbd.O)R.sup.2,
R.sup.1 and R.sup.3, independently, are selected from m-phenylene,
p-phenylene, 3,3'-biphenylene, 3,4'-biphenylene, 4,4'-biphenylene
and 4,4'-diphenylene ether,
R.sup.2 is selected from R.sup.1 and --CH.sub.2).sub.x,
Ar is 1,2,4-benzenetriyl, and
x is 1 to 10,
the polyamide having a molecular weight of at least about 2500; and
quaternary ammonium cations of the formula
wherein each R.sup.4 is independently selected from hydrocarbyl or
substituted hydrocarbyl, provided that at least one of the R.sup.4
groups contains at least one beta hydrogen atom. Also provided is a
process for producing such quaternary ammonium polyarylamides, a
process for making parts from such quaternary ammonium
polyarylamides and a process for modifying the surfaces of
polyamides.
DETAILED DESCRIPTION OF THE INVENTION
When the polyarylamide of the present invention is formed, a
hydrogen ion (proton) is removed from the amido group nitrogen atom
to form an anion. The terms polyamide and amido herein mean a
polymer and functional group (not necessarily a --C(.dbd.O)NH--
group) respectively that still has all of its hydrogens attached
(not deprotonated) to its nitrogen atoms, while the term amide
means a deprotonated functional group, and the term polyarylamide
means a polymer that is at least partially deprotonated (a
polyanion). Of course when more than one proton is removed from any
polymer molecule, a polyanion is formed. The chemistry of forming
such amide anions (with alkali metal bases) is well known to those
skilled in the art, see for example M. Takayanagai and T. Katayose,
J. Polym. Sci., Polym. Chem. Ed., vol. 19, p. 1136, which is hereby
included by reference, and is analogous to the present
reaction.
The polymers useful in this invention: for forming quaternary
ammonium polyarylamides are wholly aromatic polyamides (as in an
aramid), polybenzimidazoles, and polyureas containing the --NH--
function as part of the urea group. All of these polymers are
referred to as polyamides herein. Aromatic polybenzimidazoles
useful in this invention are described in U.S. Pat. No. 3,551,389,
useful aramids are described in U.S. Pat. Nos. 3,869,429 and
4.075,172, while useful aromatic polyureas are exemplified in U.S.
Pat. No. 3,418,275, all incorporated by reference herein. Useful
polymers include, but are not limited to, PPTA, poly(m-phenylene
isophthalamide), poly(p-benzamide), poly(4,4'biphenylene
isophthalamide), poly(chloro-p-phenylene isophthalamide),
polybenzimidazole from 3,4,3',4'-tetraaminobiphenyl and isophthalic
acid and the polybenzimidazole of 3,4-diaminobenzoic acid.
Preferred polymers are PPTA, poly(m-phenylene isophthalamide) and
poly(p-benzamide). Especially preferred are PPTA and
poly(m-phenylene isophthalamide). Block copolymers that contain one
or more blocks of the above polymers [optionally with blocks
containing other (nonpolyamide) monomer units] also are useful in
the present invention.
The quaternary ammonium cations of the present invention have the
formula
wherein each R.sup.4 group is independently selected from
hydrocarbyl or substituted hydrocarbyl provided that at least one
of the R.sup.4 groups contains at least one beta hydrogen atom. By
substituted hydrocarbyl is meant a hydrocarbyl group that contains
substituents or functional groups that do not interfere with the
formation or decomposition of the quaternary ammonium
polyarylamide, and which obviously will not make the ammonium base
used in the formation of the salt unstable. A suitable functional
group is ether (joining two segments of hydrocarbyl chains). By
beta hydrogen is meant the grouping ##STR2## wherein the "open"
bonds may be any of the groups as defined above, or parts of
carbocyclic or heterocyclic (but not aromatic) rings. It is
preferred that the quaternary ammonium cation have a molecular
weight of less than about 350, and more preferred that the
molecular weight be under 250, so that the free amine formed in the
thermal decomposition of the salt is volatile enough to vaporize
during the decomposition reaction. Preferred quaternary ammonium
ions are tetraethylammonium and tetra-n-butylammonium.
The quaternary ammonium polyarylamides may be isolated as
relatively pure compounds (but usually containing solvating
molecules such as DMSO), or be made or used in solution.
Dialkylsulfoxides are preferred solvents, and DMSO is especially
preferred.
The amido protons of the polymers may be completely reacted
("neutralized") so that essentially all of the amido groups in the
polymer are converted to amide ions, or as little as 0.1% may be
reacted. The polymer will become soluble at some intermediate value
between the two. The polyamide may be in solution at the beginning
of the process, as the reaction may be carried out by combining a
solution of the polymer with a solution of the quaternary ammonium
base. The minimum amount of reaction needed for solubility will
depend on the polymer composition, the solvent used, the
temperature, the concentration and the quaternary ammonium cation
used, and may be determined by simple experimentation. The lower
end of the range of reaction is especially useful where surface
modification of a part (e.g. film, fiber, etc.) is desirable, as
for promoting adhesion of the polyamide to itself. The proportion
of the protons removed from amido groups may be controlled by the
ratio of quaternary ammonium base (infra) to polymer (the more base
used the higher the proportion of amido groups reacted), or by
partial neutralization by a stronger acid of the quaternary
ammonium amide groups in the polyarylamide.
The process for making the quaternary ammonium polyarylamides of
the present invention comprises contacting the polyamides with a
solution of a basic compound of the quaternary ammonium ion such as
the hydroxide or alkoxide. The quaternary ammonium base is
dissolved in a solvent, and the solvent may also be a solvent for
the quaternary ammonium polyarylamide that is produced. Quaternary
ammonium bases are usually soluble in highly polar compounds such
as water or alcohols, and in dialkylsulfoxides, especially DMSO.
When making the polyarylamide it is important not to have too high
a concentration of hydroxylic compounds such as water and alcohols
present. It is understood by those skilled in the art that even
though the protons on the amido groups may be more acidic than
those in water and alcohols, a large amount of hydroxyl groups
present could shift the equilibrium so that much of the quaternary
ammonium salt present is as the hydroxide or alkoxide rather than
the polyarylamide polyanion. Excess water and/or alcohol may be
removed under vacuum at 60.degree. C. or below, preferably at about
room temperature.
Compounds which are more acidic (have a lower pKa) than the proton
on the amido nitrogen should not be present. A compilation of
acidities (pKas) of various acids in DMSO is available, see F.
Bordwell, Acc. Chem. Res , vol. 21, 456-463 (1988). It is believed
that the pKas of the amido protons of the present polymers are
about 19-29 in DMSO.
The quaternary ammonium polyarylamide may be formed at temperatures
ranging from about 0.degree. C. (or the freezing point of the
solvent, whichever is higher) to about 60.degree. C., preferably
about 20.degree. C. to about 40.degree. C. If the polymer is to be
dissolved, the overall reaction time usually ranges from about 0.5
to about 24 hr. However, this time may vary widely, depending
especially on the state of division of the polymer, the more finely
divided the polymer, the faster the dissolution. Moderate to
vigorous stirring and/or sonication is desirable to accelerate the
dissolution. Since excess water should be excluded, it is
convenient to make the polyarylamide under an inert atmosphere such
as nitrogen or argon. The starting materials should be
substantially dry (free of water), however most quaternary ammonium
bases contain some water which is difficult to remove
completely.
These bases are often available in hydroxylic solvents. In order to
keep the total amount of hydroxylic compound low, it is often
desirable to remove as much of the solvent from the quaternary
ammonium base by removing the solvent under vacuum at approximately
room temperature or below.
The quaternary ammonium bases suitable for use in this process have
the formula
wherein each R.sup.4 is independently selected from hydrocarbyl and
substituted hydrocarbyl, providing that at least one of R.sup.4
contains at least one beta hydrogen atom, and wherein X is an anion
whose conjugate acid has a pKa greater than that of the hydrogen
attached to the amido group in the unreacted polymer, in the
solvent in which the reaction is carried out. Preferred anions are
hydroxide and alkoxide. Preferred quaternary ammonium ions are
tetraethylammonium and tetra-n-butylammonium.
The quaternary ammonium polyarylamides may be isolated by removing
the solvent at reduced pressure at low temperature (less than about
60.degree. C.) or by adding the solution of the polymer salt to an
aprotic nonsolvent, thereby precipitating the polymer salt. It may
then be isolated by filtration.
Many of the above features of the above process are illustrated in
the Examples.
While the polyamide may be regenerated by reaction with acid, such
regeneration normally results in at least traces of ionic material
remaining in the polymer. In the case of the present quaternary
ammonium polyarylamides, heating of these salts can lead to
formation of the original (protonated) polyamide, along with olefin
and tertiary amine byproducts. The olefin and tertiary amine are
usually volatile, and are removed by vaporization during the
heating period.
This reaction to regenerate the original polymer on heating
(pyrolysis) is believed to be a variation of the well known (to
those skilled in the art) "Hofmann elimination." For a review of
this reaction see A. C. Cope and E. R. Trumbull, Organic Reactions,
Vol. 11, John Wiley & Sons, Inc., New York, 1960, p. 317-493.
Most Hofmann elimination reactions have been run using the
hydroxide of the ammonium cation, but other basic anions will also
work. It is believed the amide anion which is part of the polymer
chain performs a similar function in this invention.
It is also well known that the Hofmann elimination has side
reactions that compete with the "main" reaction leading to (in the
present case) the protonated amide group, olefin and tertiary
amine. The most important of these side reactions is the alkylation
of the basic anion, which in the present case would be the amide
anion nitrogen atom. The proportions of "main" reaction and
alkylation reaction depend upon various factors (see Cope and
Trumbull, supra), but especially the structure of the quaternary
ammonium cation. It is difficult to predict in advance the
proportions of such reactions when using the quaternary ammonium
polyarylamides, but Experiments 1 and 2 illustrate easily run model
reactions, where with minimum experimentation, the proportions of
these reactions can be determined for any particular quaternary
ammonium cation. Cations can be chosen to maximize either
reaction.
The regeneration of the original polymer by heating of the
quaternary ammonium polyarylamide, so that the Hofmann elimination
takes place, is a superior method than the reaction of a metal salt
of the polyarylamide and subsequent washing of the polymer, for
obtaining polymer free of ionic impurities. Furthermore, even the
"side" reaction of alkylation is useful, since alkylation leads to
polymers with modified properties, such as higher solubility, as
for coatings.
Polymers used to form the quaternary ammonium polyarylamides useful
in the pyrolysis reaction consist essentially of one or more of the
repeat units: ##STR3## wherein: R is selected from R.sup.3 and
R.sup.1 NHC(.dbd.O)R.sup.2
R.sup.1 and R.sup.3, independently, are selected from m-phenylene,
p-phenylene, 3,3'-biphenylene, 3,4'-biphenylene, 4,4'-biphenylene
and 4,4'-diphenylene ether,
R.sup.2 is selected from R.sup.1 and --CH.sub.2).sub.x,
Ar is 1,2,4-benzenetriyl, and
x is 1 to 10,
the original polyamide having a molecular weight of at least about
2500, and further providing that the quaternary ammonium ions of
the quaternary ammonium polyarylamides useful in the pyrolysis
reaction have the formula
wherein each R.sup.4 group is independently selected from
hydrocarbyl or substituted hydrocarbyl provided that at least one
of the R.sup.4 groups contains at least one beta hydrogen atom.
The pyrolysis of the quaternary ammonium polyarylamide is carried
out at about 70.degree. C. to about 300.degree. C. or the upper
temperature stability limit of the polymer, whichever is lower,
preferably about 150.degree. C. to about 300.degree. C., and most
preferably about 180.degree. C. to about 250.degree. C. Although
the pyrolysis reaction is not affected by air, use of an inert
atmosphere such as nitrogen or argon is useful where the polymer is
unstable to oxygen at elevated temperatures. The pyrolysis may be
done with neat quaternary ammonium polyarylamide or with the
quaternary ammonium polyarylamide in solution. While the pyrolysis
is taking place it is convenient to remove the solvent by
evaporation, and also remove the volatile byproducts of the
pyrolysis such as the olefin and tertiary amine. Circulation of
gases around the polymer will help remove these compounds. In
thicker sections of polymer, boiling of the solvent or rapid
production of the volatile olefin and/or tertiary amine may produce
bubbles in the polymer. Slowly increasing the reaction temperature
will help avoid such problems. The degree of deprotonation of the
polymers undergoing the pyrolysis reaction can range from 0.1% to
100%. The pyrolysis reaction is further illustrated in the
Examples.
The quaternary ammonium polyarylamides of the present invention may
be used to form films, coatings, fibers, etc., especially from
solution, that when pyrolyzed regenerate the original polyamide or
an N-alkylated polyamide with different properties than the
original polymer. In both cases the polymer is essentially free of
ionic impurities.
Solutions of quaternary bases may be used to treat the surfaces of
polyamides (without dissolution of the polymer) to increase the
adhesion of the polymer to itself or to other materials, such as
metals (see commonly assigned U.S. patent application Ser. No.
351,962, filed May 17, 1989, which is hereby included by
reference). Again, upon heating the original polyamide may be
regenerated containing essentially no ionic impurities. Surface
treatment requires only that a relatively small proportion of the
total number of amido groups in the polymer be converted to the
quaternary ammonium salt. This proportion will of course vary with
the surface to volume ratio of the particular part, but may be as
small as 0.1% of the total amount of amido groups in the polymer.
Of course for surface treatment the polymer should not dissolve in
the solvent.
EXAMPLES
In the following Examples, except where otherwise noted, the
quaternary ammonium bases were supplied by the Aldrich Chemical
Co., the tetraethylammonium hydroxide as a 40 weight percent
solution in water, and the tetra-n-butylammonium hydroxide as a
1.0M solution in methanol. DMSO was Aldrich Gold Label grade, used
without further purification. All reactions were done under a
nitrogen or argon atmosphere.
EXPERIMENT 1
A nitrogen flushed reaction flask equipped with stir bar was
charged with approximately 10 mL anhydrous DMSO and 6.40 mL of a
1.0 molar solution of (n-Bu).sub.4 N.sup.+ OH.sup.- solution in
methanol. The methanol and a small amount of DMSO was removed by
means of vacuum distillation at room temperature. C.sub.6 H.sub.5
C(O)NHC.sub.6 H.sub.4 NHC(O)C.sub.6 H.sub.5, made by the reaction
of 1 mole p-phenylenediamine with 2 moles of benzoylchloride, 1.0
g, was then added to the reaction vessel against a heavy stream of
inert gas. The resulting mixture was stirred for three hours at
room temperature. The ((n-Bu).sub.4 N.sup.+).sub.2 C.sub.6 H.sub.5
C(O)NC.sub.6 H.sub.4 NC(O)C.sub.6 H.sub.5.sup.2- salt was
precipitated in pure form by addition of approximately 100 mL of
dry diethyl ether. The salt was isolated by filtration and dried in
a vacuum for 15 hours at room temperature. .sup.1 H NMR (d.sub.6
-DMSO, +25.degree. C.): +8.05 ppm (doublet of doublets, 4H, J=7.5
hz, 2.0 hz), +7.15 ppm (singlet, 4H), +7.07 (multiplet, 6H), +3.04
ppm (multiplet, 16H), +1.48 ppm (multiplet, 16H), +1.12 ppm
(multiplet, 16H), + 0.86 ppm (triplet, 24H, J=15.9 hz). Thermal
gravimetric analysis showed loss of 55% of the mass at 179.degree.
C., for loss of butene and tributylamine, which was confirmed by
mass spectra of the volatiles evolved. A solid state pyrolysis of
((n-Bu).sub.4 N.sup.+).sub.2 C.sub.6 H.sub.5 C(O)NC.sub.6 H.sub.4
NC(O)C.sub.6 H.sub.5.sup.2- yielded extensively butylated material
as evidenced by mass spectrometry, NMR spectrometry, and infrared
spectroscopy. Both the N-n-butyl and the bis(N,N'-n-butyl)
compounds were detected.
EXPERIMENT 2
A 125 mL Erlenmeyer flask with ground glass stopper was charged
with 1.00 g C.sub.6 H.sub.5 C(O)NHC.sub.6 H.sub.4 NHC(O)C.sub.6
H.sub.5 and 10 mL of DMSO. Separately a solution of 1.00 g Et.sub.4
N.sup.+ OH.sup.- was dissolved in 10 mL DMSO. The solution frothed
considerably but the salts dissolved. The resulting solution was
combined with the slurry of the oligomer. The resulting solution
was stirred for one hour to give a homogeneous solution. 100 mL of
dry diethyl ether was added which caused formation of an oil. The
supernatant was decanted from the oil. The oil was treated with
approximately 4 mL dry tetrahydrofuran to give yellow crystals
which were isolated by filtration and dried by means of a vacuum.
The .sup.1 H NMR suggested that this compound was (Et.sub.4
N.sup.+).sub.2 [C.sub.6 H.sub.5 C(O)NC.sub.6 H.sub.4 NC(O)C.sub.6
H.sub.5 ].sup.2- with a small amount of water. The .sup.1 H NMR of
this compound in d.sub.6 -DMSO (ppm rel. to tetramethylsilane):
+8.05 (doublet of doublets, 4H, J=7.5 hz, 2.0 hz), +7.5 (singlet,
4H), +7.18 (multiplet, 6H), +3.60 (broad singlet, approx. 2H),
+3.12 (quartet, 16H, J=7.0 hz), +1.09 (triplet of triplets, 24H,
J=7.0 hz, 2.5 hz). Infrared spectra in a KBr pellet showed the
presence of N--H and O--H bonds, indicating that the oligomer was
not fully deprotonated. A solid state pyrolysis of this compound at
200.degree. C. gave C.sub.6 H.sub.5 C(O)NHC.sub.6 H.sub.4
NH(O)CC.sub.6 H.sub.5 nearly quantitatively with traces (<1%) of
N-ethylated product. A mass spectrometry/pyrolysis probe experiment
showed that triethylamine was formed in this process.
EXAMPLE 1
Preparation and Pyrolysis of PPTA
Tetraethyl Ammonium Salt
A round bottom flask was charged with 12.5 g of a 25 wt. % solution
of Et.sub.4 N.sup.+ OH.sup.- in methanol. Methanol was removed from
this solution by means of vacuum distillation until the solution
volume was approximately 9 mL. This base solution was then
transferred to a three neck flask containing 55 mL DMSO and 2.5 g
PPTA pulp. The PPTA pulp was dissolved in this medium to give a
solution that was 3.6 wt. % polymer. A film of this solution was
cast on a glass plate at 25 mil (wet thickness) under a dry
nitrogen atmosphere. The film was heated to 220.degree. C. under a
dry nitrogen atmosphere to give a dense PPTA film.
EXAMPLE 2
Preparation of the (n-Bu).sub.4 N.sup.+ Salt of PPTA
A solution (25.2 mL) of 1 molar (n-Bu).sub.4 N.sup.+ OH.sup.- in
methanol was dissolved in 65 mL DMSO. The methanol was then removed
from the solution by means of vacuum distillation. The remaining 55
to 60 mL of clear colorless solution was transferred by cannulation
to a three neck flask containing 3.3 g PPTA pulp. After 16 hours of
stirring at room temperature, the PPTA pulp was dissolved in this
solvent system to form a clear, deep red solution with no evidence
for undissolved PPTA as determined by examination of samples under
an optical microscope. A film was then cast at 25 mil (wet
thickness) on a glass plate and placed in a vacuum at 205.degree.
C. with a slow nitrogen purge. The DMSO distilled off leaving a
reddish orange film on the glass plate. After approximately 30
minutes at 205.degree. C., the reddish orange color gave way to the
tan color characteristic of PPTA films. However, the final film
after 24 hours at 205.degree. C. and under vacuum was pale tan and
very brittle, characteristic of butylated PPTA films. Infrared
spectra of this film showed the presence of alkyl groups, again
suggestive that some alkylation had taken place in addition to the
Hofmann degradation. Pyrolyses at 175.degree. C. and at 220.degree.
C. showed that butene, tributyl amine, and DMSO evolved in the
vapor phase from this reaction.
EXAMPLE 3
Bonding of PPTA Pulp Using (n-Bu).sub.4 N.sup.+ OH.sup.- Solutions
in DMSO
Ten mL of 1.0 molar (n-Bu).sub.4 N.sup.+ OH.sup.- was dissolved in
40 mL anhydrous DMSO. Methanol (approximately 10 mL) was removed
from this solution by vacuum distillation. The resulting 0.2 molar
base solution was pulled through a disk of PPTA pulp on a Buchner
funnel by means of a vacuum. The pulp was left undisturbed for one
hour. Then the pulp was pressed between two
poly(tetrafluoroethylene) sheets at 180.degree. C., initially with
no pressure to allow volatiles to escape easily, and then finally
ramped to 235.degree. C. and 172 MPa and held for 5 minutes. The
result was a low density paper like material. The tensile
properties of these pulps before and after treatment are shown
below.
______________________________________ Before After
______________________________________ Tensile Strength (MPa) 0.93
22.1 Elongation at Break (%) 11.7 8.0 Tensile Modulus 41.4 1076
______________________________________
EXAMPLE 4
Isolation of the "Neat" (n-Bu).sub.4 N.sup.+ Salt of PPTA
A nitrogen flushed three neck reaction vessel equipped with
mechanical stirrer was charged with 120 mL anhydrous DMSO and 50.4
mL of tetrabutylammonium hydroxide as a 1 molar solution in
methanol. The methanol was removed from the resulting solution by
means of vacuum distillation. Six g of PPTA pulp was added. The
pulp dissolved in 16 hours to give an approximately 4 wt. %
solution, which was optically isotropic. Twenty-one g of this 4 wt.
% solution was added slowly to approximately 500 mL of anhydrous
tetrahydrofuran with rapid stirring to give a red precipitated
solid which weighed 2.57 g after drying. This solid is
predominantly the (n-Bu).sub.4 N.sup.+ salt of PPTA, the remainder
being solvent. A sample of 1.0 g of this solid was redissolved in
2.9 g of DMSO to give a highly viscous, somewhat pasty, mixture
which flowed as a solution and was optically birefringent as
determined by optical microscopy.
EXAMPLE 5
Preparation of the (n-Bu).sub.4 N.sup.+ Salt of PPTA
To a 100 ml round bottomed flask was added 40 ml DMSO and 5 ml of a
25% by weight of tetrabutylammonium hydroxide in methanol solution
(Alfa Chemicals). The flask was connected to vacuum "ia a nitrogen
trap and warmed to .about.50.degree. C. The flask was held under
vacuum until the pressure in the flask was similar to the vapor
pressure of DMSO at 50.degree. C. (.about.5 mmHg) indicating that
the methanol had substantialy been removed. PPTA was then placed in
the flask (600 mg sifted PPTA) and the vacuum reapplied (to
continue removing residual methanol). The PPTA dissolved within 1
hour as witnessed by the simultaneous disappearance of the yellow
polymer and appearance of the characteristic red solution.
EXAMPLE 6
Preparation of the Et.sub.4 N.sup.+ Salt of Poly(m-phenylenediamine
isophthalamide) (MPD-I) and of a film Therefrom
Et.sub.4 N.sup.+ OH.sup.- (3.33 g) was dissolved in 80 mL of DMSO.
MPD-I (2.01 g) was then added and the resulting slurry was stirred
for one week at room temperature. The resulting solution was
filtered through glass wool to remove a trace of insoluble species.
Under a dry nitrogen atmosphere, several drops of the solution were
placed on a glass slide which was then heated on a hot plate to
210.degree. C. to give an MPD-I film with an infrared spectrum
identical to authentic MPD-I.
* * * * *